1. Technical Field
The present invention relates to a relative angle sensing device and an electric power steering apparatus.
2. Related Art
Recently, there has been suggested a device for sensing a relative rotation angle between two rotary shafts coaxially arranged.
For example, a device described in Japanese Patent Application Laid Open Publication No. 2007-187589 includes: two magnetic-flux collecting rings provided outside of and away in an axial direction from magnetic circuit forming components held by a first rotating body and a second rotating body coaxially coupled to each other by a torsion bar, the two magnetic-flux collecting rings collecting a magnetic flux generated by the magnetic circuit forming components; a detection unit that detects torque added to the first rotating body based on a density of magnetic flux collected by each of the magnetic-flux collecting rings; a holding ring that holds the magnetic-flux collecting rings and the detection unit, and has an attachment portion on a circumferential portion thereof attached to a housing; and a conductor wire connected to the detection unit. The detection unit is configured so that a detection signal is changed in accordance with change of the density of magnetic flux generated between protruding pieces of the magnetic-flux collecting rings, and the detection signal is provided to a controller constituted by a microprocessor through the conductor wire.
In a case where a configuration is such that a sensor (the detection unit) contained in the housing and a device provided with the detection signal from the sensor and arranged outside of the housing are connected with electric cables (conductor cables) held by an electric cable holding member (a grommet) inserted into a through hole of the housing, even if a force is applied to the electric cables at the outside of the housing, there is a possibility that a large force is applied to end portions of the electric cables at the inside of the housing. For example, in a case where the end portions of the electric cables are coupled to a connector inserted into a connecting terminal, there is a possibility that the electric cables detach from the connector or the connecting terminal into which the connector is inserted is broken when the large force is applied to the end portions of the electric cables at the inside of the housing. Additionally, due to the force applied to the electric cables at the outside of the housing, there is a possibility that sealing properties of the electric cables in the electric cable holding member (the grommet) are deteriorated.
On this problem, it is considered to prevent detachment of the electric cable holding member (the grommet) inserted into the through hole formed in the housing and to support the electric cables by arranging a plate made of a sheet metal at the outside of the housing, for example. However, in this configuration, if the housing is made of aluminum, there is a possibility that the electric cable holding member (the grommet) detaches due to electrochemical corrosion caused between the plate and the housing. In addition, the number of assembling process is increased for arranging the plate outside of the housing.
An object of the present invention is to suggest a device that realizes, with a simple configuration, an intention not to exert a large force on the electric cable holding part in the electric cable holding member and the end portions of the electric cables inside of the housing even though a force is exerted on the electric cables at the outside of the housing.